Dehydrator



Jan. 10, 1939.

w. A. ARNOLD DEHYDRATOR Filed Sept. 14, 1936 M NYENTOZ4 B M, MLJM/ W ATTORNEYS Patented Jan. 10, 1939 UNITED STATES PATENT OFFICE 2,143,505 nnnrnns'ron William A. Arnold, Wauwatosa, Wis. Application September 14, 1936, Serial No. 100,623

12 Claims. (01. 24-24) This invention relates to improvements in dehydrators.

It is the primary object of the invention to provide an improved control for the prevention of overheating of material in a dehydrating apparatus, particularly during intervals when a. supply of fresh material being fed into the apparatus is either uneven; entirely interrupted, or is of varying moisture content.

More particularly stated, I propose to provide improved and practicable means for the controlled recirculation of a portion of the moisture laden or humid gases which have already passed through the apparatus and which are substantially free of oxygen, such gases being admitted in substantial quantities to the apparatus only in the event that overheating occurs, but being maintained as nearly as possible a relatively cool and oxygen-free gas for the purpose of advancing and cooling the material in the drying drum in constant motion through the pipe."

Another very important object of the invention is to provide a series of controls graduated as to their eflect for reducing temperatures in emergencies, first by the admission of cooler gases to the machine, and secondly by the direct injection of water into the path of the dehydrating gas. Other objects will appear from the following disclosure, including the provision of a control system capable of adjustment to maintain proper balance in the drying chamber. 1

In the drawing:

Figure 1 is a fragmentary view in side elevation of apparatus embodying the invention.

Figure 2 is a fragmentary detail of the furnace in transverse section on an enlarged scale.

Figure 3 is a detail view on an enlarged scale partially in side elevation and partially in axial section showing the point at which the control is preferably operative. v

Like parts are identified by the same reference characters throughout the several views.

The dehydrating cylinder t may be of any desired type, its interior construction being broadly immaterial to the present invention. It is suggested that it may be of the type shown in the patent to Gerald D. Arnold, No. 1,988,677. It

preferably rotatable and provided with a stationary input at and a stationary discharge port at t. In the preferred connection between the respective throats and the cylinder each of the may he provided, as shown in Fig. 3. with an annular diaphragm ll en aged in an annular channel 3 which connected by ring 5 with a drum t to rotate therewith. Such a joint is easily packed and is maintained tight by air pressure and is readily accessible for repair or for the diassembly of the parts of the apparatus.

The dehydrating drum t is supplied through the intake throat 5 with highly heated dehydrating gasses by means of a furnace l preferably having a refractory lining at H and a spaced jacket l2 which not only insulates the furnace but conserves the heat. Preferably the interior of the furnace is cylindrical in form, and by way of illustration I have shown it heated by a gas burner 53 supplied with fuel through a pipe It controlled by a valve i actuated by diaphragm IS in the manner hereinafter to be described.

The air to be carbureted by the burner i3 is admitted through duct l I under control of dampers I8. Additional air admitted to the jacket space I!) under the control of damper passes completely about the furnace as indicated by the arrows in Fig. 2, and enters through a tangential duct 2! preferably located immediately below the burner so that the greater weight of the relatively cool air thus admitted will enable it to be centrifugally maintained separate from the products of combustion, whereby to form a blanket for the protection of the refractory lining H. In passing from the furnace, however, the air thus admitted and the products of combustion are thoroughly intermingled.

As the hot gases pass through the port 5 the material to be dehydrated is fed by a rotary charging device into their path, and the material is thus projectd into the dehydrating drum.

As the dehydrated material and the products of combustion leave the drum they are acted upon by a centrifugal blower fan 26 which keeps the entire drum and furnace under partial vacown. The blower elevates the material through pipe 2'! to centrifugal separator 2d from the bottom of which the dehydrated material issues through the sacking pipes 29, and from the top of which the dehydrating gases issue through vent til.

In accordance with the present invention I I provide a cap 3! over the rent 3%, and connect a return pipe 32 which leads to an air chamber 33 below intake throat and communicating therewith subject to the control of damper 3t. l lihere any other inert and relatively cool gas isuch. for example, as nitrogen or carbon dioxide) available for the purpose, I should regard as to deliver such gas through pipe it in stead of gas returned from the vent 3B. A bypass pipe 35 of small capacity leads from the chamber 33; to the jacket space it within the 2 I furnace jacket II, this by-pass being controlled by a damper 36.

At some convenient point, as for example the spout of the charging device, I provide a spray head 38 supplied with water through pipe 39 controlled by a valve 40 which is subject to the action of a diaphragm in chamber 4| operated by means now to be described.

On the outlet throat 6 I provide, preferably but not necessarily, a plurality of thermostats which are set for successive operation. '(One thermostat of special construction may perform the several functions to be described.) The thermostat 44'is connected by pipe 45 with a diaphragm l6 which operates the fuel valve l5. This same diaphragm actuates 'a lever 66 adjustably connected to rock shaft 41 which opens and closes dampers i8 and 2B. This same rock shaft may be provided with linkage for the operation of dampers 34 and 36 in mutually opposite direc-' tions, damper 34 being arranged to close as dampers 20, I8 and3ii open. Damper 3E operates in unison with dampers. i8 and 20 to open and close as they open and close, and as the fuel valve l5 opens and closes.

The second thermostat is connected by pipe ill with diaphragm 4| which controls the water valve 40, it being understood that any appropriate liquid may be evaporated instead of water, provided it will not leave a taste in the product. Water serves every purpose and is inexpensive and most readily available. The two supply lines controlled by thermostats 44 and 50 for energizing the diaphragm valves are fed by a pressure line 52, using any suitable gas or liquid for the energizing medium. I

During normal operation of the dehydrator the parts wili'not be in the position shown in the drawing. Damper 34 will be closed and damper 36 open. Dampers I8 and 20 and valve IE will likewise be open. Theair supplied through dampers I8 will take care of the proper functioning 'of the burners, and the resulting gases, tempered by air admitted through the chamber, which is first passed completely around the jacket of the furnace, will be delivered through the throat 5 of the dehydrator across the path of the material admitted to the charging device 25.

The suction produced in the dehydrator by means of the exhaust fan and casing 26 will not only draw fresh air into the apparatus through the dampers l8 and 20, but will also recirculate a portion of the gases already used for dehydration, such gases being substantially free of oxygen and relatively cool upon their release from the separator 28. The recirculation of such gases through pipe 32 is permitted by damper 38 which opens just sufficiently wide to keep pipe 32 warm so that no great amount of condensation will occur in such pipe as would be the case if the pipe were cold at the time damper 34 was opened. It will, of course, be understood that damper 34 remains closed until overheating occurs.

Ifoverheating occurs for any reason as, for

example, due to irregular feeding or cessation of feeding, or change in moisture content of the material fed, the thermostat 44 will first respond to energize diaphragm i6 and thereby to partially or largely close the fuel'valve i5 and the corresponding shutter valves I8, 20 and 38, and concurrently to open the damper 34 which will admit the return gases to the dehydrating chamher without first passing them through the furnace. The capacity of the opening controlled by damper 34 will preferably'be sufficient to subperatures in the dehydrating apparatus but keeping gas flow substantially constant therein.

The retention of the hot gases in the furnace dueto the closing of shutter valves i8, 26 and 36, will enable the heating operation to be resumed without any temperature lag such as would otherwise be required to heat up the furnace.

If the temperature in the output end of the apparatus continues to rise, the thermostat 56 will now respond to energize diaphragm 3i and to open valve lil so as to spray water from pipe 39 and spray head 38 directly into the charging throat. A very small amount of water is sufficient, because of its evaporation, to effect a very substantial reduction in temperature. At intervals when no material is being fed through the charging'device, as is always the case in shutting down the machine, the thermostat may be adjusted to feed the same amount of water which the dehydrating gases would otherwise evaporate from the normal flow of hay or other material through the apparatus, thus compensating exactly for the decreased supply of material to be dehydrated. This operation will continue until all of the remaining material is discharged from the apparatus, and in the use of the device it has been found possible to shut down without so much as scorching the last vestiges of material passing through the machine.

Assuming the shut-down to have been temporary, the renewed feeding of material through the charger will, by evaporation of its moisture, tend to reduce the temperatures in the apparatus, thus affecting the thermostats 50 and 44 which will function successively in the order named to relieve the pressure on the respective diaphragms 4i and I6, resulting in first closing the water valve 40 and subsequently, if the temperature continues to decrease, closing valve 34 and opening valves I8, 20 and 36. The drawing shows the several parts as they appear during the maximum overheat permitted by the apparatus. The operation of the thermostatic conin the event of rise of the temperature from that predetermined, mechanism controlled in the first operation of said means for tempering dehydrating gases-in said chamber, and mechanism controlled in the subsequent operation of said means for admitting free water to such gases.

2. Dehydrating apparatus including the combination. with a dehydrating chamber, a furnace, and means for propelling dehydrating gases from said furnace through said chamber. of an admission port for tempering gases, a. damper controlling said port, a water supply pipe having its have passed at least part way through said chamber and provided with control mechanism operatively connected for automatically actuating said damper and said valve successively to open positions upon a continued rise of temperature in said chamber.

3. A dehydrating system comprising the combination with a dehydrating chamber, of means for supplying a substantially constant circulation of gases through said chamber for the pneumatic propulsion therethrough of the material to be dehydrated therein, said gas supply means including a heater, means including a damper for passing air directly to said chamber or deflecting it through said heater, whereby to control its temperature without substantially affecting its volume, and a thermostat exposed to the dehydrating gases and operatively connected with said damper for the regulation of the position thereof. i

4. A dehydrating system comprising the combination with a furnace having a combustion chamber, a jacket and an intervening space, said chamber being ported for communication with said space and said space having an exterior port communicating directly with. the atmosphere, means for causing the air in said space to pass, about said combustion chamber between said ports for the preheating thereof, a damper controlling the flow of air, a dehydrating chamber provided with means afiording communication from said combustion chamber, a thermostat, and actuating means controlled thereby for operating said damper, said dehydrating chamber having a discharge throat adjacent which said thermostat is located, means for withdrawing gases from said throat, a separator into which said last mentioned means discharges, a return pipe from said-separator to the jacket space of said furnace, and a by-pass from said pipe ef fording access ofrecirculated gases to said dehydrating chamber independently of said combustion chamber, said by-pass having a damper operatively connected to be actuated from said thermostat. V g

5. Dehydrating apparatus comprising the combination with a dehydrating chamber and means for supplying thereto a material to be dehydrated and a dehydrating gas, of means for automatically regulating temperatures in said, chamber, said means including a water admission port in the path of said gas adjacent the entrance to said chamber, a thermostat in the path of the gas which has acted on material in said chamber, a valve controlling the flow oi water through said port, and mechanism operatively connecting the thermostat with said valve for the actuation thereof in a direction to open said valve upon an excessive rise of temperature of the gases to which said thermostat is exposed, whereby to tend to control by evaporation the temperature of such gas prior to its substantial dehyd'rating action upon the material within the chamber.

6. Dehydrati'ng apparatus comprising the combination with a dehydrating chamber and means for supplying thereto a material to be dehydrated and a dehydrating gas, or means for discharging free water into the path of said gas, valve means for controlling the flow of water. and means including a thermostat exposed to gases which have acted on such material in the dehydrating chainand thermostatic means exposed to gases which her and operatively connected to said valve means for automatically increasing the flow of water as the flow of material to be dehydrated is reduced.

7. Dehydrating apparatus comprising a furnace having a combustion chamber, a jacket space, a. jacket, a first port leading directly to said combustion chamber, a duct leading from the jacket space into the combustion chamber, an exterior second port leading into the jacket space 10 and communicating with the duct therethrough, and a burner arranged to receive air through the first mentioned port, of dampers controlling the first port and the exterior port and connected to operate concurrently in their opening and closl5 ing movements, a valve controlling the burner and connected with said dampers to open and close in accordance with the movements thereof, a dehydrating chamber, a. throat affording communication between the furnace combustion chamber and the dehydrating chamber, means for circulating gases from thefurnace through the dehydrating chamber, and a thermostat exposed to such gases and provided with means controlling the operation of said dampers and valve 25 as aforesaid. I

8. Dehydrating apparatus comprising a furnace having a combustion chamber, a jacket space, a jacket, 2. first port leading directly to said combustion chamber, a. duct leading from 30 the jacket space into the combustion chamber, an exterior second port leading into the jacket space and communicating with the duct therethrough, and a burner arranged to receive air through the first mentioned ports, ofdampers controlling the 35 first mentioned port and the exterior port and connected to operate concurrently in their opening and closing movements, a valve controlling the burner and connected with said dampers to open and close in accordance with the movements thereof, a dehydrating chamber, a throat affor-ding communication between the furnace combustion chamber and the dehydrating chamber, means for circulating gases from the furnace through the dehydrating chamber, and a thermostat exposed to such gases and provided with means controlling the operation of said dampers and valve as aforesaid, together with a separator connected with said gas circulating means and having a discharge vent, a recirculating pipe lead- 50 ing from said vent to said throat, and a damper controlling communication between said pipe and said throat and operatively connected to be opened and closed oppositely to the movement of the dampers aforesaid 9. Dehydrating apparatus comprising a furnace having a combustion chamber, a, jacket space, a jacket, 2. first port leading directly to said combustion chamber, a duct leading from the Jacket space into the combustion chamber, an exterior second port leading into the jacket space and communicating with the duct therethrough, and a burner arranged to receive air through the first mentioned ports, of dampers controlling the first mentioned port and the exterior port and 65 connected to operate concurrently in their openmeans controlling the operation of said dampers and valve as aforesaid, together with a separator connected with said gas circulating means and having a discharge vent, a recirculating pipe perature of said gases.

10. A method of dehydration which inciudes'the feed.ing of material to be dehydrated into the path of dehydrating gases, the continued advance of gases on said path, and the delivery of free water to said gases in advance of their substantial dehydration of such material and in inverse ratio to the amount of material fed.

,11. A method of dehydration which includes the feeding of material to be dehydrated into the path of dehydrating gases, the continued advance of gases on said path, and the delivery of free water to said gases in advance of their substantial dehydration of such material and in inverse ratio to the amount of material fed, and the regulation of the rate of feeding such water in quantities to compensate for the decrease of evaporatable water in the decreasing amounts of material.

12. A method of dehydration which includes the establishment of a continuous current of dehydrating gases, the delivery thereto of material to be dehydrated, and the delivery of free water into the path of said gases: and said material in advance of substantial dehydration of said material, said delivery of water being conditioned upon the occurrence of rise of temperature of gases which have acted on such material.

. WILLIAM A. ARNOLD. 

